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Questions Re: Adding Lights, Forced Air Heat, General Wiring in Attic

Questions Re: Adding Lights, Forced Air Heat, General Wiring in Attic

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  #1  
Old 11-12-10, 07:21 PM
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Questions Re: Adding Lights, Forced Air Heat, General Wiring in Attic

I'm finally going to add forced air heating to my home. I'm consulting with a licensed heating contractor but I try not to bug him with questions every day, especially with regard to the finer electrical details. I have done such installs before, but because this is a two unit building in my jurisdiction the homeowner can't pull a permit. It was a huge disappointment to find that out a few years after buying the place. So really I'm paying him to double check my work and pull the permit, not teach me the trades,

I've been doing electrical work for 25 years and can read code, but I have a horrible memory so if you don't mind I'll pick your brains here for a few details. My copy of the NEC is so old it fits in my back pocket (though I'm aware you can get it online for free at this point.)

A number of years ago I used the existing knob and tube wires(!) to pull NM throughout the premises, running each branch through the attic. I read up on it a bit, and gave it some Deep Thought. I ended up running the NM across the joists a few feet from the rafter plates, as this gave enough access for servicing but was inconvenient enough to dissuade anyone from storing stuff there. Even if I converted it to living space, it's most common to drop vertical walls a few feet high and leave the space behind as triangular "crawlspace," and transforming the living space from a triangle to a pentagon.

Admittedly I left a few mechanical details to do "later". At one point there was an indication that I needed to lay down "running board" under the NM.

Is that true? Do I need to underlay the wiring or can I staple it directly to the joists? Is there a minimum width of the underlayment?

As I recall the joists are on 16 inch centers. Do I have to staple each wire to each joist, or can I skip N joists before securing?

I've subsequently heard that there's some sort of 5 foot rule, WRT the attic entrance maybe? Or maybe from the nearest flooring used for storage or walkways?

Can you give me some details on this 5 foot rule?

Now that I'm putting the heater up there, I need a switched attic light(s). At first I thought it would be cool to recess the switch (pilot lighted) into the floor near the entrance. But I couldn't really find any support for the idea in the marketplace and I've since decided its not practical, not a particularly good idea, and probably prohibited by code. True on all counts?

The lightswitch must be within 12" or 24" or accessible (I do have the figure somewhere) from the attic opening.

I think the most common solution is to use a 2X4 from one of the joists up to a rafter and mount the switch on that. Can I run NM along this post? It would seem to violate the 5 foot rule, if such rule exists. Note the temptation to grab this post could be very strong, as it is you have to hoist yourself up the last foot or so by grappling the edges of the access hole. But as I recall from the field, this is common and almost anything goes in the attic.

Most of the treatments of the ligthswitch issue seem to assume the switch will be mounted inside the attic. Can I mount the switch in the ceiling of the residential space below, near the attic opening? Mostly curious. I'd do it but the attic access "door" is a wood frame multi-pane (no lead) stained glass window, and there's a skylight above. It attracts attention and I don't necessarily want to spoil the "look". Note well there are no stairs to/in the attic, folding or otherwise. Entry requires an A frame ladder. Note also the ceilings are 11+ feet high.

OK next option: mount the switch on the wall within N inches of the attic opening.
Why not? Would the "usual" limits on lightswitch heights apply? Presumably you'd only need access to the switch when you wanted to access the attic, and you'd need the ladder anyway...

Next: mount the switch at a normal height below the access door. Would that violate the N inches rule? That idea has advantages and disadvantages. Perhaps the best advantage would be that you could illuminate the stained glass at night for a nice effect.

Sounds like overkill, but would it be necessary to meet code to use a three-way configuration if I wanted the illumination and also meet the N inch rule? Maybe I should see it as two separate projects, a dedicated light fixture for the aesthetic effect with a switch mounted at normal height, and a switch for code-compliant illumination purposes inside the attic. Certainly the first light would help you find the interior switch.

Finally, the pull-chain switch. Is that still legal? All of the pullswitches I have seen are either integrated into the fixture or designed as replacements for same. But I assume I want more than one fixture in the attic. Ignoring for a moment the idea of having a pullchain for each fixture, it raises the issue as to whether or not the switch is rated for the current of more than one fixture. I've seen switches rated at 6 amps. Can I assume each fixture will draw 100 watts max, thus allowing for as many as 7 fixtures? If not, what safety factor should I use? Would the code even allow a pullswitch built into a fixture to be used to control other fixtures? How about if I used a replacement pullswitch, drilled a hole for it in a blank plate, and mounted it in a box. Could I then use it to control multiple fixtures? Are there special built, heavy duty pullswitches designed for general purpose applications?

Before we leave the subject of NM and lighting.... I can run NM up the rafters and along the roof ridge board to supply my lighting fixtures, correct? Does this depend on whether or not I use the attic for storage? The ridge is about 7-8 feet from the top of the joists.

I'd like to put an outlet or two up in the attic while I'm at it. I haven't looked into that yet so I don't have any questions to ask, except for this:

I don't want to tie the outlets into the lighting circuit. I try to keep my light circuits separate from outlets, my thought being if you pop a breaker you should have a well lit path to the breaker box. This would be especially true in the attic.

A dedicated circuit is needed for the forced air heater. Could I put a "3 way" (SPDT) switch at the the heater itself, such that in one position it energized the heater, and in the other position it energized a (very) nearby outlet? It'd be kinda cool, if you wanted to vacuum out the heater such an arrangement would help ensure the power to the heater was off while you worked on it. I'd say "Of course not!" but recently an inspector told me of an installation he'd seen (or heard about) where a 3-way switch was used in a dishwasher/garbage disposal scenario. I didn't ask (dang) but I think he implied it passed. In one position the circuit was "dedicated" to the GD, in the other dedicated to the DW. Heh.

An awful lot of questions, I know, but the answers would help me tie up a lot of subtle loose ends. And since these posts seem to stick around forever, maybe help a few chaps down the road.

Thanks in advance!

-Jeff
 
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  #2  
Old 11-15-10, 09:26 AM
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Originally Posted by mysterylectric View Post
At one point there was an indication that I needed to lay down "running board" under the NM.
If the NM is in an accessible area of the attic then it needs to run inside the framing cavities or along a running board like a 2x4. If the attic has stairs then all romex needs to be protected with running boards. If it only has a scuttle hole, then only romex within 7' of the hole or in areas where the height is high enough that a person could be walking needs to be protected. I would nail a 2x4 across the joists and run the romex in the "L" between the 2x4 and joists. The idea is to make the running board take the impact from a footstep so the cable doesn't get squished.

Do I have to staple each wire to each joist, or can I skip N joists before securing?
NM needs to be stapled every 54" or run through bore holes in the framing.

At first I thought it would be cool to recess the switch (pilot lighted) into the floor near the entrance.
I don't think there are any floor-rated switch plates, so probably not possible to do to code.

I think the most common solution is to use a 2X4 from one of the joists up to a rafter and mount the switch on that. Can I run NM along this post?
Just make it so the cable is protected from damage and it will be okay. You can make a notch or a groove to run the cable in or run it through a short length of PVC conduit if necessary.

Can I mount the switch in the ceiling of the residential space below, near the attic opening? Mostly curious.
I don't see why not; you could mount it at regular switch height in the wall too. I suppose a picky inspector would demand the switch be close to the attic door, but since there is no permanent access to the attic I think a normal height switch on the level below would be acceptable.

to use a three-way configuration if I wanted the illumination and also meet the N inch rule?
You could put them in parallel so if either switch is on the light is on. That would prevent a prankster from turning off your light while you were up there working. He could still steal your ladder though...

I can run NM up the rafters and along the roof ridge board to supply my lighting fixtures, correct?
I don't like this idea because roofers drive nails like crazy -- dangerous place to have NM.

A dedicated circuit is needed for the forced air heater. Could I put a "3 way" (SPDT) switch at the the heater itself, such that in one position it energized the heater, and in the other position it energized a (very) nearby outlet?
No the code requires a dedicated circuit for the heater and also a service outlet (on a different circuit) within 25' of the HVAC.
 
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